No gods is the most important decision so far. How the DS team handles the "planes" will also be vital.
Well, the planes are kind of an odd duck IMO. I don't remember the planes being very vital to DS at all, except for the elemental cosmology. Still, those were more forces to worship than places to visit.
Now, I do remember a module with a planar invasion of Githyanki. But that was just a weird one...
They better be careful about how they include all the various 4e races.
I expect you'll see them, but I expect they'll be intensely modified, flavor-wise. I don't think WotC is going to release a setting which says "YOU MAY NOT PLAY A GNOME" nowadays. I think they
might say "Gnomes are intensely unusual on Athas. You might be the only one. Also, you eat people" or something like that.
Campaign crunch from the Forgotten Realms and Eberron settings must NOT be included in the setting. Period.
I don't expect it will be referenced at all. So I wouldn't expect to see stuff about Artificers or Dragonmarks. But I also wouldn't expect to see something like, "You may not have a Dragonmarked character in your game."
Paladins do not belong in Dark Sun; however, I have a feeling that the class will get shoe-horned into the setting.
I think 4e Paladins can fit very well into Dark Sun. It wasn't the class that didn't work for 2e; it was the Lawful-Goodness of the class. At least IMO. An Unaligned paladin serving Primordials could work decently well. So just because 2e DS had no Paladins doesn't mean 4e DS shouldn't; a 4e paladin is not a 2e paladin.
Bards need to be assassin-like. Dark Sun bards are NOT happy lute-stumming minstrels.
I think the DS version of Bard is very well-served by both the new Assassin class (as previewed), and the existing 4e Rogue. Whether or not there will be a place for the PHB2 arcane leader called the "Bard" remains to be seen. Again, just because the poison/assasin/minstrel character was called a Bard under 2e doesn't mean a character filling the same niche in 4e must also be called a Bard.
Dune Trader should be a class and there must be an option for players who want to be a gladiator in the Dark Sun-style.
I wouldn't hold my breath for a base Dune Trader class. It'd be cool, but I dunno. I think there should be a Dune Trader paragon path, though.
-O